There has been developed a head-mounted display that a user wears on the user's head to view a video or the like. In the future, in viewing a video or the like, the user is expected to switch between a display device such as a television (TV) receiver, a display, and a mobile terminal for the user to view the video at a distance, and the head-mounted display that the user wears on the head to view the video. It is conventionally known that the user switches a video output by switching between a stationary display device of a TV receiver and a portable display device operated at hand by the user such as a portable game machine and a tablet terminal.